The Panama Basin is a miniature ocean basin in which the effect of variable rates of supply, dilution, dissolution, and lateral transport of biogenous sediments can be studied in detail. The rate of input inferred from rates of biologic productivity in surface waters does not resemble the distribution of either carbonate (foraminifera and calcareous nannofossils) or opal (diatoms and radiolaria) in sediments at the sea floor. The distribution of carbonate is primarily controlled by dissolution ; at any depth, the rate is highest adjacent to the continent and decreases offshore in the more pelagic areas. The rate of dissolution increases rapidly with depth at about 1,500 m. Winnowing and lateral transport from ridges into the basin is the second most important factor controlling the distribution of carbonate and the dominant factor governing the distribution of opal. In pelagic sediments of the western basin, about half the carbonate fraction appears to be derived from the surrounding ridges. Dilution by terrigenous material is important only in the eastern Panama Basin, where the concentration of opal is significantly reduced by fine-grained debris derived from Central America.